In a recent patent by the inventors, a novel optical weighing system was disclosed which provides extremely fast and accurate means for measuring product weights on the fly. The invention discloses optical measuring techniques to determine the deflection of elastic members loaded by the product being weighed as it moves past one or more sensing stations.
Disclosed herein is an extension of this concept, together with others, to the automatic control of filling machines. The particular embodiments disclosed are useful in the bottling and packaging industries but it is clear that the concepts here apply to any sort of fill in which a container is filled with a substance.
The general category in which the improvements here disclosed are of use is entitled "Fill and Weigh" or "Weigh and Dump". Typical prior art U.S. patents in this are are: Nos.
4,230,195, which teaches a servo-mechanical check weigh feedback filler for liquids PA1 3,805,903, which teaches control algorithims for effective feedback of check weigher data to a filling machine or machines PA1 3,339,651 disclosing a vibratory filler operable by tipping or increasing vibrator rate to deposit over or under weight recepticle batches in a reject area, with acceptable batches going to containers. Vibration is idle during a check weigh phase. PA1 2,603,442, disclosing a bag filler wherein the input of bulk item flow is shut off when a desired bag weight is reached. PA1 1. In-process weighing of the container being filled near the end of the filling process to stop the process or determine if an additional amount (eg. "dribble", typically 5%) is required. Of particular interest here are those weighed on-the-fly, ie. at high speed. PA1 2. In-process filling by weight of batches, receptacles etc. of material previous to dumping said batch into a container. This also is usually done in motion in a high speed system. PA1 3. Filling by any convenient means, including volumetric, with post process monitoring (ie. check weighing) the weight of the filled packages and feeding back deviation data to controls on the filling machine. PA1 provide a means to monitor empty (tare) weights of containers at high speed to provide a true fill weight, PA1 provide means to monitor individual weights at high speed in continuous rotary motion. PA1 provide means to safely monitor dry product and other explosive material weights remotely with computer compatable outputs, PA1 provide total computer auto calibration of weigh pan and/or container each cycle, PA1 provide for operation with multiple types of containers in the same machine, even intermixed, PA1 provide for weight measurement of parts such as cartridge cases, pen refills etc. placed into spring clips, magnetic holders or the like, PA1 provide for ink jet coding of weight, date shift etc. information at high speed, PA1 provide for enhanced performance with vibratory fill systems, PA1 provide a unique ferris wheel or vertical rotary scale arrangement usable for scooping up product or vertically transfer any products, PA1 provide a vastly simpler mechanical apparatus than all known prior art, resulting in much less maintenance, with far higher rates.
The above prior art references generally disclose means for doing the following:
In each of the above, the accuracy of weighing required limits the speed of the process, conversely, high speed limits accuracy. Improvement of such accuracy, particularly at the high speeds needed to achieve today's productivity requirements is the primary goal of this invention.
In addition, the invention discloses novel embodiments which:
It is the first intention of this invention to show means for improving the weight measurement capability of weighing type filling machines such as that described above, utilizing the concepts in our own weigh scale U.S. Pat. No. 4,216,837.
A second goal of this invention is to illustrate means for accurately weighing the container before fill as well as during or after fill such that the weight of the container can be removed from the weight calculation to allow a true calculation of net weight.
A third purpose of this invention is to illustrate improved means for monitoring weight throughout the filling cycle but particularly near the end of the cycle when a last topping-up or "dribble" type fill is provided. This utilizes continuous reading optical principles which may also be used in applying our weight scale patent.
Finally, application to both linear and rotary type scales is illustrated. Together with all the concepts above, a truely accurate weight based fill is possible for the first time in general not requiring additional compensating equipment after filling machine and completely obviating the historical difficulties with complex mechanical linkages, motions etc.
The further result of the above invention and improvements is the achievement of considerably higher filling rates under total control together with higher accuracies.
Additionally illustrated in this disclosure are further methods for controlling filling machines also electro-optically sensor based. These include automatic fill heighth detection by both transmited and reflected light means, and automatic optical flow meter controlled volumetric fill (the level detection also being a type of volumetric fill. Other means may also be utilized separately or in concert with the weigh based portion of the invention.
Another major advantage of the invention is that unlike those balance type units illustrated in the above references, this particular invention monitors over the total fill or at least has the capability thereof. Typically one has historically monitored only at the end, namely when the container is nearly filled. However, the advantage to monitoring over the total fill cycle is first to be able to weigh the container and second, to be able to measure the performance of the filling unit as a function of time. This can tend to allow prediction of the final fill condition and act as a further predictor of potential maintenance problems such as clogging, intermitent spurts etc. All of these plug the ability of the computer to track the performance of the machine allows for a much more easy to maintain machine.
The ease of maintenance also comes from the fact that in the prefered embodiment, the weigh members are load cells rather than balances and are vastly stiffer and without moving parts. This increased stiffness allows a much higher fill rate of the machine since for any given accuracy level, the vibrations of the machine or of the fill itself are not transmitted to the cells as readily as they are in the balance type machine. This of course is where the bottom line of most filling operations is, once a correct scheme for obtaining legal weight has been established. Naturally, the ability to hold the low limit of the legal weight allows a saving in material as well.
The very stiffness and extremely high resolution of the all optical non-contact readout further adds to accuracy allowing the cells herein to be both more accurate and capable at higher speeds than any previous design known. This is certainly true at least when one considers those which could be easily implemented on the filling machine whose very operation virtually requires a non-contacting type of readout.
As mentioned in the aforementioned patent by the inventors, the microcomputer of the readout (itself optional) may be used to track the individual cell constants and zero settings and actually a rezeroing process can occur each cyle of the machine by simply measuring the weight with no container at all on it after unloading. This of course is not at all possible with the machines as shown in the art and leads to the requirement for having to have a separate tracking system for adjusting calibration such as shown in U.S. Pat. No. 4,230,195.
Furthermore, any inputs from the outside such as provided by an operator etc. may be made electronically and are not required to be made mechanically, thereby eliminating large sources of error and maintenance problems.
The other interesting advantage of this machine is its ability to automatically and trivially account for changes in product. For example, it really doesn't matter what weight is desired in a package to be filled or what the package weight itself is, as long as it is within the range of the scale. Therefore one can change products, or fill levels, or containers, without really doing anything with the scale other than dialing in the settings desired, in net weight. This is a significant user benefit since typically highly skilled labor is required to set up such machines and this obviates the requirement therefore.